1. Field of the Invention
The present invention relates to high solids low-temperature curable resinous compositions. More specifically, the invention relates to resinous compositions containing allylether-functional unsaturated polyester-urethanes.
2. Brief Description of the Prior Art
For a number of coating applications, there are employed low-temperature curable two-package systems containing active hydrogen-functional materials and isocyanate curing agents. However, due to health-related problems associated with exposure to, and unsafe handling of isocyanates, two-package systems containing isocyanates are becoming less attractive. Hence, there is a need for alternate curable compositions which cure at ambient or low temperatures.
There is a particular need for high solids low-temperature curable compositions that can be applied to thermally sensitive materials, such as plastics and woods, and other materials which are not conducive to high-temperature cure. High solids compositions are particularly desirable since these coatings usually contain reduced quantities of volatile organic contents (VOC). The present invention provides for high solids curable compositions containing allylether-functional polyester-urethanes.
Art-related compositions which have been suggested for use as low-temperature curable compositions differ from the composition of this invention. Illustratively, in U.S. Pat. No. 4,005,041, allylether-functional polyurethanes, described therein, are very limited in scope. They are prepared with glycerol derivatives with secondary hydroxy groups and hydroxy-functionality greater than two. The polyurethanes derived therefrom can be made only with isophorone diisocyanate, perhaps because of the selectivity afforded by the isophorone diisocyanates. The use of other isocyanates are said to result in gelation. In contrast, in the present invention, a variety of isocyanates can be employed in preparing the polyurethanes without gelling the resultant product.
Also, the allylether-functional polyurethanes, described in U.S. Pat. No. 4,005,041, are of a nature that gives them a prescribed solubility in solvents with Kauri-Butanol (KB) values of less than 40. Apparently, hydrophobic groups associated with glycidyl esters, used therein, contribute to the prescribed solubility of these polyurethanes. In another contrast, the allylether polyurethanes of the present invention are of such a nature that makes them relatively insoluble in solvents of such low KB values.